This invention relates to fuel pumps, and particularly to a fuel sender unit that is submerged within the fuel tank of a vehicle. More particularly, this invention relates to a fuel sender unit that is automatically movable to reach lowermost regions of a vehicle fuel tank during fuel sending activity to maximize fuel recovery from the fuel tank.
Many vehicle fuel tanks, particularly those made of plastics material, tend to sag under a full fuel load. plastic fuel tanks are widely used on light duty trucks, vans, and also on some passenger cars. Over time, the permanent shape of such a deformable fuel tank changes as it is continually exposed to cyclic loading and stretched beyond its elastic limit. Fuel collecting in depressed regions of the fuel tank is often inaccessible to conventional fixed-position fuel pumps. Typically, conventional fixed-position fuel pump systems are unable automatically to reach and pump fuel that collects in these low-lying sagging regions of deformed fuel tanks.
Once installed, conventional fixed-position and extensible fuel pump systems are not easily adjusted to compensate for variation in fuel tank shape due to sag. Another problem is that conventional fixed position and ( extensible fuel pump systems are not easily converted for installation in fuel tanks of different sizes, shapes, and depths. Instead, it is generally necessary to produce a separate fuel pump system of a particular size matched to accommodate a fuel tank having a designated shape and size.
Interrupted fuel supply to a fuel pump is a another significant problem hampering operation of vehicles, especially those vehicles equipped with a fuel injection system. In particular, a vehicle fuel pump can suddenly go "dry" whenever the fuel level in the fuel tank is too low as a result of fuel sloshing and churning during swift vehicle cornering maneuvers or other agitation of the fuel tank. In conventional carbureted engine systems, the carburetor includes a fuel reserve float bowl for supplying fuel to the engine until the fuel pump resumes delivery of fuel from the fuel tank. By comparison, the engine in a vehicle having a fuel injection system will stop whenever the delivery of fuel from the fuel pump is interrupted. Serious accident or injury can result from a momentary lapse in engine operation caused by an interruption in the supply of fuel to the fuel pump.
A fuel sender apparatus adapted to reach and pump fuel collected in low-lying sagging regions of a fuel tank and also configured to accumulate fuel in an auxiliary fuel reservoir within the fuel tank to maintain an uninterrupted supply of fuel to the fuel pump would avoid serious shortcomings of conventional fuel pump systems.
According to the present invention, a fuel sender unit is provided for delivering fuel from a conventional fuel tank that may have a resilient bottom wall that deflects under a fuel load. The fuel sender unit includes a support fixture mounted on the fuel tank, sending means within the fuel tank for pumping fuel in the fuel tank toward a point of use outside the fuel tank, and extensible means for coupling the sending means to the support fixture for relative movement therebetween in response to fuel pressure generated during operation of the sending means. Thus, the sending means is lowerable to a variety of depths within the fuel tank to reach and pump fuel accumulating in various regions along the bottom fuel tank wall notwithstanding any sagging deformation of said bottom wall.
One feature of the present invention is the provision of extensible means for coupling the fuel sending means for relative movement within the fuel tank in response to fuel pressure generated during operation of the fuel sending means. This feature positively positions the fuel intake portion of the fuel sender unit to set flush on the bottom of the fuel tank. Thus, one fuel sender unit advantageously fits fuel tanks of different size. In addition, such an extension capability advantageously enables the sending means to reach and pump fuel accumulating in low-lying regions of a sagging fuel tank bottom wall while fuel is being pumped from the fuel tank. This feature greatly enhances operation of fuel sending units submerged in fuel tanks, particularly those fuel tanks tending to sag or change shape under a full fuel load.
In preferred embodiments, the sending means includes a reservoir cup for accumulating an auxiliary supply of fuel within the fuel tank and a fuel pump having its inlet in fluid communication with the reservoir cup. The reservoir cup is suspended in its various operating positions within the fuel tank by the extensible means. Fuel inlet means is provided in at least one of the cup walls so that fuel is admitted into the reservoir cup after the crest of fuel in the fuel tank has fallen to a level below a maximum capacity level established by an upper annular edge of the reservoir cup. It is important to keep the fuel pump "wet", i.e., in fuel. The reservoir is self-filling and stays full even when the vehicle is cornering and fuel is low.
The extensible means provides means for guiding the sending means along a path toward the bottom wall of the fuel tank. The guide means desirably includes a siphon tube for selectively conducting fuel from the reservoir cup to locations outside of the fuel tank and a return tube for delivering fuel to the reservoir cup from a source outside the fuel tank. In one embodiment, the return means interconnects a fuel injection system and a reservoir cup so that uncombusted fuel discharged by the fuel injection system during operation of the vehicle is returned to the reservoir cup for recirculation to the engine
Fuel discharge means is provided for conducting fuel discharged from the pump outlet under pressure toward a point of use outside of the fuel tank. The fuel discharge means is configured to provide adjustment means for yieldably biasing the pump and reservoir cup assembly against the bottom wall of a fuel tank during fuel pumping activity to maximize recovery of fuel from the fuel tank.
Illustratively, the adjustment means includes a fixed hollow discharge tube extending through an aperture in the support fixture and a companion movable hollow discharge tube. An upper end of the movable discharge tube is slidably received within the fixed hollow discharge tube in telescoping relation and a lower end of said movable tube is rigidly connected to the pump outlet. The upper end of the movable discharge tube includes an annular biasing surface received in a hollow space in the fixed discharge tube. That hollow space is pressurized by fuel discharged under pressure therethrough by the pump.
In operation, pressurized fuel in the hollow space acts on the annular biasing surface to apply a downwardly-directed force causing the movable discharge tube to slide downward relative to the fixed discharge tube. This sliding movement lowers the pump and reservoir cup assembly, and in particular, the fuel inlet means of the reservoir cup, to a lowest operating position with the fuel tank in close proximity to the bottom wall of the fuel tank.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.